anti-Vibrio Activity Research Articles

Green synthesis and evaluation of dual herb-extracted DHM-AgNPs: Antimicrobial efficacy and low ecotoxicity in agricultural and aquatic systems

Uncontrolled applications of weedicide and fertilizer can harm the soil ecology, and most significantly, earthworms are hazardous soil engineers. Thus, we aimed at the toxicity and histopathological alterations in the earthworm Eudrilus euginae following exposure to glyphosate (weedicide), urea (fertilizer), and environmentally friendly dual herb-mixed silver nanoparticles (DHM-AgNPs). The DHM-AgNPs were synthesized using a blend of Alfinia officinarum and Curcuma longa aqueous leaf extracts with 1 mM silver nitrate. The color change from yellow to brown after an hour of incubation was a significant indicator of successful DHM-AgNP synthesis. Characterization of the DHM-AgNPs using UV–Vis spectra indicated a surface plasmon resonance (SPR) peak at 430 nm. In addition to FT-IR spectroscopy and XRD analysis, SEM, TEM, and SEM investigations were performed to identify the DHM-AgNPs. The XPS analysis revealed the oxidation state and surface chemical composition, and Ag NP's specific surface area and degree of porosity were measured using BET. Furthermore, different concentrations of urea and glyphosate were administered to Artemia nauplii and E. euginae to assess their toxicity. The mortality rate for E. euginae exposed to a higher urea concentration (10 g/kg of soil) was 100%. In contrast, a % mortality rate of 83% was noted at 0.5 g/kg of soil. The maximum mortality (90 ± 0.64%) was observed at a 10 mL/kg/L concentration for glyphosate. In contrast, low mortality was noted in E. euginae and A. nauplii exposed with gradient concentrations of DHM-AgNPs compared to glyphosate and urea. As aquaculture and foodborne diseases are widespread, DHM-AgNPs showed significant anti-Vibrio activity against pathogenic Vibrio-related bacteria, inhibiting 80% at 100,100 μg/L, which is of great concern. This study suggests the potential use of DHM-AgNPs in field aqua and crops culture for eco-friendly pest control and anti-Vibrio activity without causing soil and environmental pollution. Further research is warranted to determine the efficacy, safety, and cost-effectiveness of DHM-AgNPs in aqua and agricultural practices.

Millmerranones G, a meroterpene isolated from a mangrove-derived fungus Aspergillus sp. GXIMD 03004

One new meroterpene derivative, millmerranones G (1), and three known analogues (2–4) were identified from the mangrove-derived fungus Aspergillus sp. GXIMD 03004, which was isolated from the leaves of mangrove Acanthus ilicifolius L. collected from Beibu Gulf in China. The structure of 1 was characterised by a comprehensive interpretation of the NMR spectroscopic and HRESIMS data. The absolute configuration for 1 was established using experimental and calculated ECD data. The anti-Vibrio activities of all compounds were evaluated, the result showed that compounds 1 and 2 has weak activity against Vibrio harveyi.

Fermentability assessment of selected oligosaccharides by Lactiplantibacillus plantarum BIOTECH 1074 towards short-chain organic acid production with anti-vibrio efficacy

Vibriosis, caused by Vibrio harveyi and Vibrio parahaemolyticus, poses a significant threat to aquaculture, resulting in substantial economic losses. Oligosaccharides are known for their ability to improve gut health and prevent vibriosis in aquaculture species. This study explored the fermentative utilization of galacto-oligosaccharides (GOS), manno-oligosaccharides (MOS), and inulin by Lactiplantibacillus plantarum BIOTECH 1074. GOS and glucose were the preferred substrates for L. plantarum growth, producing high levels of lactic acid, propanoic acid, and acetic acid. These compounds showed substantial anti-Vibrio activities, having inhibitory concentration values of 0.252 ± 0.005 and 0.656 ± 0.015 mg total organic acid/mL against V. harveyi, V. cholerae, and V. parahaemolyticus from GOS fermented supernatant. The fermentative capabilities of L. plantarum BIOTECH 1074, in utilizing specific oligosaccharide substrates to produce organic acids with anti-Vibrio potential, offers a promising strategy for enhancing disease management and overall efficiency in aquaculture systems.

Isolation and Molecular Identification of Termite Nest Associated Bacteria with Potential as Vibriosis Biocontrol Agents in Shrimp Farming

The potential for aquaculture development in Indonesia, especially the shrimp farming industry, is projected to continue to increase. However, the current growth in aquaculture production is in line with the increasing number of disease outbreaks and can affect the production, profitability, and sustainability of the industry worldwide. Vibriosis is a major challenge in aquaculture that causes fish mortality in large numbers and rapid times. Vibriosis treatment is still limited to the same antibiotics in humans and animals. For this reason, alternative microorganisms that are more specific and selective in inhibiting vibrio are needed, one of which is the exploration of termite nest association bacteria. This study aims to obtain isolates of termite nest association bacteria that are antivibrio. Isolation of bacteria using ISP2 media. Furthermore, antagonistic screening was carried out against V. alginolyticus and V. harveyi bacteria. Isolates performed morphological and biochemical characterization followed by molecular identification with 16s rRNA sequence analysis using universal primer 27F 1492R. Isolation results obtained 15 isolates with varying colors and shapes. Ten isolates are Gram-positive bacteria and 12 isolates have a positive catalase test. Seven isolates have antivibrio activity, namely isolates SR9, SE1, SE4, SE5, SE6, SE7 and SE8. Isolate SE1 showed the best antivibrio activity capable of inhibiting the growth of V. alginolyticus and V. harveyi bacteria with an inhibition zone value of 3.5 cm and 4 cm, respectively. The results of the molecular analysis showed that isolate SE1 has 99.65% similarity with Bacillus amyloliquefaciens strain HY2-1. These bacteria have characteristics that have the potential to be used as probiotics in the aquaculture industry, especially vibrio biocontrol agents.

Synthesis and Anti-Vibrio Activity of Gallic Acid Derivatives Containing Acyl Thiourea Phenol

Synthesis and Anti-Vibrio Activity of Gallic Acid Derivatives Containing Acyl Thiourea Phenol

Impact of THIONIL® on reducing water and soil micro-pollutant and enhancement of growth, survival, anti-vibrio, immunity and health indices of Litopenaeus vannamei in pond trial.

There is an urgent requirement for the improvement of the white leg shrimp, Litopenaeus vannamei; health-related indices; and immunity due to emerging diseases. Recently, probiotics have been playing an important role in L. vannamei health management. Therefore, the current pond trial was to evaluate the probiotic proficiency of commercial probiotic products of THIONIL (THIO) on the enhancement of the water, soil, growth, digestibility, survival, immune-related indices, and susceptibility of L. vannamei to infection. The study was carried out in the major shrimp culturing regions of Kavali, Nellore (Andhra Pradesh), and Ponneri (Tamil Nadu), India. Six groups (lacks/ha) of the experimental L. vannamei were allocated, including a control group (THIO 0%-untreated) and groups containing 2%, 4%, 6%, 8%, and 10% of THIO that were encapsulated with commercial feed (CP Aqua). Bioassays were performed on PLs/ shrimp at various days interval of 0, 5, 25, 50, 100, and 123th to assess productivity, anti-vibrio activity, and digestive enzyme for digestibility, histological and immunological indices, and cytotoxicity in Artemia nauplii. Significant differences were observed in the increased growth (35.71 ± 3.24g/shrimp) and digestive parameters in 10% THIO-fed shrimp. Although in contrast to the control group, the other THIO-fed prawn groups also displayed appreciable development. The findings showed that, in comparison to the control, the gill, hepatopancreas, and stomach had reduced tissue damage with 10% THIO. Furthermore, Vibrio parahaemolyticus (0.008 × 104cfu/g) and Vibrio harveyi (0.051 × 105cfu/g) (vibriosis) were potentially resistant to the 10% THIO-fed group. In addition, THIO-fed prawns (10%) showed significant improvements in immune-related expresses (proPO, SOD, and SOA) in comparison to the control. In conclusion, the findings showed that the THIO treatment prawns significantly improved the quality of their water (pH, ammonia, nitrogen dioxide, hydrogen sulfide, and DO) and soil (Pb, Cr, Hg, Mg, Cu, Fe, and Ni), increased and demonstrated protection against vibrio infections.

Bioactive Compounds in Nest-Associated Bacteria Termites and Their Bioactivity as Antivibrio in Aquaculture Industry

Abstract Vibriosis is a major problem in aquaculture that causes large numbers and rapid mortality of fish. Vibriosis treatment is still limited to the same antibiotics in humans and animals. This study aims to obtain bacterial isolates from termite nests that are antivibrio and determine the profile of the antivibrio bioactive compounds. Bacterial isolates were obtained from three types of termite nests. All isolates were cultured on ISP media and then characterized and conducted bioassay tests against Vibrio alginolyticus and Vibrio harveyi. Secondary metabolite fermentation products from selected bacterial isolates were extracted using ethyl acetate and detection of bioactive compounds by Thin Layer Chromatography (TLC) method. The isolation results obtained 15 isolates, 10 Gram-positive bacteria namely isolates SR1, SR2, SR8, SR9, RE2, RE3, RE5, SE1, SE4, SE6 while the other 5 isolates are Gram-negative bacteria. Antivibrio screening obtained 7 isolates that have antivibrio activity. The strongest antivibrio activity is SE1, which was able to inhibit the growth of V. alginolyticus bacteria with an inhibition zone of 3.5 cm and V. harveyi with an inhibition zone value of 4 cm and was also positive for catalase. TLC showed that SE1 contained peptide compounds with purple color changes after dyeing using ninhydrin.

Synthesis and Anti-Vibrio Activity of Some New 1,3,4-Thiadiazole Derivatives Containing 7-Aminocephalosporanic Acid

A series of new 7-aminocephalosporanic acid containing 1,3,4-thiadiazole derivatives (8a-f and 9) was synthesized in search of potential antibacterial agents. These structures were characterized by means of infrared, proton nuclear magnetic resonance, and electrospray ionization-high-resolution mass spectrometry. All the tested compounds demonstrated good inhibitory effects on anti-Vibrio activity. Among them, the minimum inhibitory concentration values of compounds 8a, 8c, 8d, and 9 against Vibrio harveyi and Vibrio parahaemolyticus reached 0.0039 mg/mL and 0.0078 mg/mL, respectively, showing better inhibitory activities even more than the standard seven streptomycin sulfate (0.016 mg/mL and 0.0625 mg/mL). Thus, these new compounds could serve as potential candidates to become leads for the development of new drugs eliciting anti-Vibrio agents effect.. KEYWORDS :1,3,4-Thiadiazole, 7-Aminocephalosporanic acid, Anti-vibrio activity.

Structural diversity and biological activities of indole-diterpenoids from Penicillium janthinellum by co-culture with Paecilomyces formosus

Co-culturing the marine-derived fungi Penicillium janthinellium with Paecilomyces formosus led to the isolation of nine new indole-diterpenes, janthinellumines A–I (1–9), along with twelve known analogues (10–21). The chemical structures including their absolute configurations of them were assigned by the analysis of extensive spectroscopic data and calculated ECD and VCD methods. These indole-diterpenoids displayed extensive biological activities, including anti-influenza A virus, protein tyrosine phosphatase (PTP) inhibitory, and anti-Vibrio activities. Among them, the anti-influenza mechanism of compounds 1, 2, and 7 was further investigated using neuraminidase inhibitory assay, molecular docking, and reverse genetics methods, suggesting that 1, 2, and 7 could interact with Arg371 of the viral neuraminidase. The structure–activity relationship (SAR) of PTPs inhibitory activity for indole-diterpene derivatives (1, 2, 4, 5, 9–16, and 19–21) was also summarized.

Antibacterial polyketides and ascochlorins from deep-sea cold-seep-derived fungus Furcasterigmium furcatum (syn. Acremonium furcatum)

Three new secondary metabolites, including a new polyketide, acrefurcatone A (1), a new ascochlorin analogue, acremochlorin N (2), and 3-phenylcyclopentane-1,2-diol (±-3), a pair of new naturally occurring enantiomers, along with nine known ascochlorins (4–12), were identified from Furcasterigmium furcatum CS-280 (syn. Acremonium furcatum CS-280), a fungus isolated from the deep-sea cold-seep sediment samples collected in the South China Sea. Their structures were determined by detailed interpretation of NMR spectroscopic and mass spectrometric data. The relative configurations of compounds 1–3 were assigned by NOESY correlations combined with gauge-independent atomic orbital (GIAO) NMR shift calculations and DP4+ probability analysis, while their absolute configurations were assigned by time-dependent density functional (TDDFT) ECD calculations and specific rotation calculations. Compound 1 exhibited potent activity against the human pathogenic bacterium Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) value of 8 μg/mL. The isolated ascochlorins also showed potent activities against aquatic bacteria, especially for Vibrio harveyi and V. alginolyticus, with MIC values comparable to chloramphenicol. Analysis of the structure-activity relationship indicated that the cinnamate derivative, such as compound 1, or the presence of chlorine atom in ascochlorin derivatives, such as compounds 4, 6, and 7, significantly enhanced the antibacterial activities. This is the first report of anti-Vibrio activities for ascochlorin derivatives.

In Vivo Anti-Vibrio Evaluation of Sponge-Associated Bacteria on the Survival Rate of Litopenaeus vannamei Infected with Pathogenic Vibrio Species.

Sponge-associated bacteria are considered a rich source of bioactive compounds particularly to reduce the risk of Vibrio harveyi and Vibrio parahaemolyticus infection. The present study aimed to analyse the effectiveness of 19 isolates to control Vibrio infection in vivo. All 19 isolates displayed a non-pathogenic characteristic on shrimps (cell density of 106 cells/mL) as analysed using the pathogenicity test. The mortality caused by both Vibrio spp. on 50% of the shrimp population (LC50 value) had a cell density of 105 cells/mL as determined using the proportion interval method. On the basis of the challenge test, all isolates improved the survival rate of infected shrimps in diverse effectivities up to 89%, which was nearly 30% higher than the infected control. Two isolates coded as D6.9, and P5.20 reduced shrimp mortality after infection with Vibrio spp. 16S rRNA-based identification showed these isolates were closely similar to different genera of Bacillus and Staphylococcus. The extract derived from the most prospective isolate, D6.9, was dominated by 1-hydroxy-6-(3-isopropenyl-cycloprop-1-enyl)-6-methyl-heptan-2-one, hexadecanoic acid, 4-epicyclomusalenone [(24S)-24-methyl-28-norcycloart-25-en-3-one], and 2,4-dimethyl acetoacetanilide. This observation suggested these isolates characterised by in vivo anti-Vibrio activity need to be further developed as biocontrol candidates.

Molecular Identification and Biotechnological Potential of Cerithidea cingulata-and Lottia scabra Associated Fungi as Extracellular Enzyme Producer and Anti-Vibriosis Agent

Mangroves are complex, unique, and dynamic ecosystems that host organisms that have special physiological adaptations to fluctuations in salinity, temperature, and pH. Gastropods have an important role in the mangrove ecosystem for food cycles and webs by helping to provide nutrients and micro-habitats for microbes. Micro-fungi isolated from mangrove ecosystems are productive sources of enzymes and bioactive compounds such as antibacterial and antifungal. In this study a explored the enzymatic and anti-vibrio activity of fungi associated with the marine gastropod Cerithidea cingulata and Lottia scabra. collected in three mangrove forests in North Sulawesi, Indonesia. The fungi associated with the specimens were inoculated on malt extract agar (MEA) using the tapping method. Enzymatic and anti-vibrio assays were conducted applying the plug method. Positive effects of the fungal compounds on Vibrio were indicated by clear zones formed around the isolates. A total of 13 fungal species were isolated from C. cingulata (19MB-C5 and 19MBa-A4) and L. scabra (19MT-07 and 19MT-18). Most fungal isolates have moderate growth rate. The isolate with highest cellulolytic, proteolytic, and anti-vibriosis activity (Vibrio parahaemolyticus, V. harveyi, V. vulnificus, and V. alginolyticus), derived from C. cingulata 19MB-C5 was closely related to Aspergillus niger, as revealed by molecular analysis using the universal primers ITS1 and ITS4 (similarity value 99%). A. niger 19MB-C5-3 has potential as a bioremediation and anti-vibrio agent that can be applied in aquaculture.

Characterization and antivibrio activity of chitosan-citral Schiff base calcium complex for a calcium citrate sustained release antibacterial agent

Vibrio parahemolyticus is the “Number one killer” of seafood products. Anti-vibrio agents having low cost and high-safety are urgently needed to supplement the application needs. This work attempted to prepare CS-CT-CCa complex with citral (CT), chitosan (CS) and calcium citrate (CCa) as raw material by microwave-assisted high-pressure homogenization. Additionally the coordination structure and morphology of Bridge-CS-CT-Schiff base/OH-CCa were verified. The prepared CS-CT-CCa had a well-dispersed property (the size: 3.55~9.33 μm and the zeta potential: +38.7~+67.5 mV) and an excellent sustained released ability (sustained release up to 180 min). MIC, Glucose assay, MDA assay, biofilm formation inhibition assay, SEM, swimming and swarming motility assay demonstrated that CS-CT-CCa had strong (MIC of 128 μg/mL) and sustained (more than 12 h) inhibitory effects against V. parahaemolyticus. Meanwhile, CS-CT-CCa could increase the membrane permeability of V. parahaemolyticus and inhibit their biofilm-forming ability in a dose-dependent manner. It could be inferred that the antibacterial activities against V. parahaemolyticus caused inhibition of biofilm formation, swimming and swarming motilities. This study provided necessary data for the further design and development of chitosan antibacterial agents, food and feed additives.

Antibacterial and antioxidant activities, lethality assay and chemical profile in crude extract of Biancaea sappan (L.) Tod. for anti-Vibrio agent

Background and objectivesThe bacterial infections are still an important cause of death for organisms leading to interesting finding the new antibacterial agent from natural source. The antimicrobial activity of Biancaea sappan extract (BSE) has been reported with a few mentions of anti-Vibrio efficiency. In this study, the heartwood extract from B. sappan was investigated for antibacterial activity, stability, toxicity, and anti-Vibrio in seawater. MethodsThe BSE was tested for antimicrobial activity to determine the minimum inhibitory concentration and minimum bactericidal concentration (MIC&MBC). The crude extract was evaluated an antioxidant activity through 2,2–diphenyl–1–picrylhydrazyl (DPPH) radical scavenging capacity and content of total phenolics according to Folin–Ciocalteu colorimetric method. Next, the BSE was determined thermal, diluent stabilities and Artemia salina toxicity before the time–kill study for anti-Vibrio in seawater. The major components in extract were analyzed using LC-Q-TOF-MS/MS. ResultsBSE was yielded at 9.56 %. The lowest MIC and MBC were 0.49 mg/mL for V. parahaemolyticus TISTR1596. The TPC in BSE was 31.46 GAE/g, and antioxidant activity with a 50 % inhibitory concentration (IC50) of 0.288 mg/mL. TPC in BSE was stable at high temperatures, and distilled water (>90 %).It was non-acute lethality toward A. salina for 24 h (LC50 = 7.374 mg/mL). At 3MIC and 4MIC of BSE were effective for killing V. parahaemolyticus within 2 h. ConclusionsThe BSE showed an effective inhibitory against V. parahaemolyticus with the lowest MIC and MBC. The TPC was stable with non-acute toxic effects on A. salina. It showed high potential anti-Vibrio activity in seawater that may be shown the usefulness in controlling Vibrio infection.

Anti-vibriosis bioactive molecules from Arctic Penicillium sp. Z2230

Vibrio species (Vibrio sp.) is a class of Gram-negative aquatic bacteria that causes vibriosis in aquaculture, which have resulted in big economic losses. Utilization of antibiotics against vibriosis has brought concerns on antibiotic resistance, and it is essential to explore potential antibiotic alternatives. In this study, seven compounds (compounds 1–7) were isolated from the Arctic endophytic fungus Penicillium sp. Z2230, among which compounds 3, 4, and 5 showed anti-Vibrio activity. The structures of the seven compounds were comprehensively elucidated, and the antibacterial mechanism of compounds 3, 4, and 5 was explored by molecular docking. The results suggested that the anti-Vibrio activity could come from inhibition of the bacterial peptide deformylase (PDF). This study discovered three Penicillium-derived compounds to be potential lead molecules for developing novel anti-Vibrio agents, and identified PDF as a promising antibacterial target. It also expanded the bioactive diversity of polar endophytic fungi by showing an example in which the secondary metabolites of a polar microbe were a good source of natural medicine.Graphical

Proteus mirabilis ( MJA 2. 6S ) from saline‐tolerant tilapia exhibits potent antagonistic activity against Vibrio spp., enhances immunity, controls NH 3 levels and improves growth and survival in juvenile giant tiger shrimp, Penaeus monodon

Of several isolates from saline-tolerant tilapia exhibiting anti-vibrio activity, an isolate that demonstrated inhibitory activity with the biggest zone of inhibition against the shrimp pathogens, Vibrio harveyi and V. parahaemolyticus were chosen and investigated in this study. The isolate showed significant inhibition against the shrimp pathogens, V. harveyi and V. parahaemolyticus in a competitive assay. Upon 16S rRNA sequencing, the isolate was identified as putative Proteus mirabilis (MJA 2.6S). P. mirabilis (MJA 2.6S) exhibited extracellular protease, cellulase and amylase activities. Pathogenicity tests showed that it was not pathogenic to the shrimp even at the highest concentration of 108 CFU ml−1. Further, P. mirabilis (MJA 2.6S) improved growth and survival, stimulated higher phenoloxidase and bactericidal activities in the shrimp host and protected it from V. harveyi experimental infection. In addition, the isolate P. mirabilis (MJA 2.6S) significantly reduced the ammonia level of the pond water samples in vitro. Taken together, the results clearly showed the strong probiotic potential of P. mirabilis (MJA 2.6S) in shrimp and hence further studies are needed to determine its wider application as a probiotic in P. monodon culture.

Isolation, Screening, and Active Metabolites Identification of Anti-Vibrio Fungal Strains Derived From the Beibu Gulf Coral.

The Beibu Gulf harbors abundant underexplored marine microbial resources, which are rich in diversified secondary metabolites. The genera Vibrio is a well-known pathogenic bacterium of aquatic animals. In this study, 22 fungal strains were isolated and identified from the Beibu Gulf coral via the serial dilution method and internal transcribed spacer (ITS) sequence analysis, which were further divided into three branches by phylogenetic tree analysis. The crude extracts of them via small-scale fermentation were selected for the screening of inhibitory activity against Vibrio alginalyticus, Vibrio coralliilyticus, Vibrio harveyi, Vibrio parahaemolyticus, Vibrio owensii, and Vibrio shilonii. The results showed that eight fungal extracts displayed anti-Vibrio activity via the filter paper disk assay. Several of them showed strong inhibitory effects. Then, two tetramic acid alkaloids, equisetin (1) and 5′-epiequisetin (2), were identified from Fusarium equiseti BBG10 by bioassay-guided isolation, both of which inhibited the growth of Vibrio spp. with the MIC values of 86–132 μg/ml. The scanning electron microscope results showed that cell membranes of Vibrio became corrugated, distorted or ruptured after treatment with 1 and 2. Taken together, this study provided eight fungal isolates with anti-Vibrio potentials, and two alkaloid-type antibiotics were found with anti-Vibrio effects from the bioactive strain F. equiseti BBG10. Our findings highlight the importance of exploring promising microbes from the Beibu Gulf for the identification of anti-Vibrio for future antibiotic development.

COMPARATIVE STUDY ON THE INVITRO ANTIBACTERIAL ACTIVITY OF SELECTED MEDICINAL PLANTS AGAINST PATHOGENIC VIBRIO SPECIES FROM DISEASED PENAEUS MONODON (FAB)

The pathogenic Vibrio sp. were isolated from diseased shrimp of Penaeus monodon (FAB) using TCBS agar medium by streak plate method. Acalipha indica (L), Vinca rosea (L), Embilica officinalis (G), Ocimum sanctum(L) and Lucas aspera (L) medicinal plants are one of the most commonly used natural antimicrobial agents used traditionally. Hence an attempt has been made to screen the antivibrio activity of some selected medicinal plants against pathogenic Vibrio sp by disk diffusion method. Among the five plants tested, water extract of Lucas aspera showed the maximum zone of inhibition against Vibrio cholerae (18±3.4 mm in diameter) and the alcohol extract showed the maximum zone of inhibition against Vibrio harveyi (NL) (16±3 mm in diameter).

Culture optimization to enhance carotenoid production of a selected purple nonsulfur bacterium and its activity against acute hepatopancreatic necrosis disease-causing Vibrio parahaemolyticus.

Purple nonsulfur bacteria (PNSB) were investigated for their carotenoid production and anti-vibrio activity against acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio parahaemolyticus. To test carotenoid production, selected strains were cultivated in basic isolation medium (BIM), glutamate acetate medium, G5 medium and artificial acetic acid wastewater (AAW) medium. From 144 PNSB, Rhodopseudomonas palustris KTSSG46 was selected to produce carotenoids under microaerobic light conditions in BIM. When the culture medium was optimized, strain KTSSG46 grown in BIM modified with l-glutamate at 1g/L more effectively inhibited AHPND-causing V. parahaemolyticus strains than standard BIM with 1g/L (NH4 )2 SO4 . BIM was further modified with 1.23 g/L MgSO4 ·7H2 O and carotenoid production increased 40.22%. Carotenoid production at day 2 by strain KTSSG46 grown in BIM modified with l-glutamate at 1 and 1.23g/L MgSO4 ·7H2 O was the same as production in BIM modified with monosodium glutamate (MSG). Culture supernatants from all BIM formulations showed similar activity against the resistant AHPND strain SR2. Based on high-performance liquid chromatography, carotenoids of strain KTSSG46 might be canthaxanthin. Grown in BIM modified with MSG, strain KTSSG46 could produce inexpensive carotenoids and release anti-vibrio compounds that, applied as shrimp feed additive, would prevent AHPND strains.

Anti‐ Vibrio activity of Pseudoalteromonas xiamenensis STKMTI.2, a new potential vibriosis biocontrol bacterium in marine aquaculture

We isolated Pseudoalteromonas xiamenensis STKMTI.2 from the mangrove sediments of Setokok Island, Indonesia. This study aimed to identify the bacterium, investigate antagonistic properties and minimum inhibitory concentration, and detect the active compounds using gas chromatography–mass spectrometry. The bacterium was identified using a biochemical test and 16S rDNA sequence analysis. Bioactive compounds were extracted from culture supernatant using EtOAc and examined for antibacterial activities against Vibrio spp. on Zobell 2216E agar medium. The antagonistic test of STKMTI.2 against Vibrio harveyi was conducted for 48 h. Active extracts were purified using preparative layer chromatography and tested for MIC. The anti-Vibrio compound was analysed using GCMS. This bacterium was found to be closest to P. xiamenensis Y2T, based on the 16S rDNA sequencing analysis. Anti-Vibrio compound was produced after 96 h of incubation. Strain STKMTI.2 inhibited 50% of the pathogenic Vibrio growth in the co-culture test. The substances in the partially purified sample detected by the GCMS analysis included triethoxy-borane; 1,3-diphenyl-1,3,5,5-tetramethyl-cyclotrisiloxane; 1,6-diazaspiro (4.4) nonane-2,7-dione; and 1,3-bis (4-methoxyphenyl)-5-phenyl-1,3,5-triazinane-2-thione. These substances showed much higher activity against Vibrio spp. compared with commercial antibiotics having MIC ≤0.78 µg ml−1. This study provides a new report on the anti-Vibrio activity of P. xiamenensis STKMTI.2.